Teenagers with severe antisocial behaviour have difficulty recognising facial expressions and are less likely to look at people's eyes, a study has found.

Researchers used eye-tracking methods to investigate why teenagers with conduct disorder have difficulty in recognising different emotions in others.

Symptoms of the disorder, which is thought to affect at least 5% of school-age children, range from truancy and lying to physical violence and weapon use.

Children with conduct disorder were found to have more difficulties in recognising emotional facial expressions compared to their typically-developing peers.

The study, by the University of Bath and the University of Southampton, also found teenagers with conduct disorder were less likely to look in the eye region of the face.

When they did look at the eyes, which are critical in communicating how people are feeling, they still found it more challenging to recognise emotional expressions.

It is hoped the study, published in the Journal of Child Psychology and Psychiatry, could lead to new treatments for children and young people with the condition.

Dr Graeme Fairchild, of the University of Bath's Department of Psychology, said: "We found that boys and girls with severe antisocial behaviour find it difficult to recognise negative facial expressions - particularly angry, disgusted, and fearful faces - and look less at the eye region of the face when trying to recognise facial expressions.

"These findings could lead to the development of new treatments aiming to enhance emotion recognition and empathy or even prevention programmes for at-risk children."

Those with the condition - particularly boys - struggled to recognise emotional facial expressions in both images and video clips.

Conduct disorder is poorly understood and thought to be under-diagnosed and often untreated, the researchers say.

It differs from more well-known behavioural conditions, such as attention deficit hyperactivity disorder (ADHD), although many children suffer from both at the same time.

Dr Nayra Martin-Key, of the University of Southampton, said: "This is the first study to combine an emotion recognition task with eye-tracking methods to examine recognition of, and attention to, facial expressions in boys and girls with conduct disorder.

"We found that having conduct disorder and being male led to a 'double-hit' - the boys with conduct disorder found it hardest to recognise emotional faces and were least likely to look at the eyes of the faces, whereas the typically-developing girls were the best at emotion recognition and fixated most on the eye region of the face.

"This suggests that interventions designed to improve emotion recognition might need to be tailored according to gender, with boys with conduct disorder needing a longer or more comprehensive intervention than girls."

The study involved 50 young people with conduct disorder and 51 who were typically-developing. Participants were aged between 13 and 18.